The present invention relates to a copy sheet stacking apparatus, and, more particularly to a copy sheet stacking apparatus that controls a lead edge trajectory path of a sheet as it exits a print area in order to prevent the back of the exiting sheet from affecting the front of a previously deposited sheet whose recorded image may not be completely dry.
Commercial copiers and printers typically have two copy sheet stations, a first paper feed station for feeding copy sheets into a path which carries the sheet through an image recording station, and a second sheet station where the output prints carrying a recorded image are conveyed and deposited. A particular problem for printers which form images by depositing ink into the recording zone (e.g. thermal and piezoelectric ink jet printers) is the smearing of ink on a sheet previously deposited in an output tray by the sliding contact of the leading edge of the subsequently exiting sheet. If the printer output rate is slow enough, this may not be a problem. However, as output copy rates increase, the ink smearing problem becomes more significant. Various approaches to alleviating this smearing problem are known and practiced in commercial printers and in the prior art. HP Deskjet 500 ink jet printers incorporate a minimum time delay into the system before sheets are deposited by suspending the printed sheets on opposed support rails which are subsequently withdrawn to allow the sheet to fall onto a previously deposited sheet. This process, as disclosed in detail in U.S. Pat. No. 4,728,963, requires a relatively complex mechanism, which adds to the printer cost. Another alternative is to select a fast drying ink; however, such inks may not be the most appropriate ink for a particular printer design. A still further approach, which adds to the cost and complexity of the system, is the use of a heating device to dry the ink on the printed sheet.